1. Field of the Invention
This invention relates to a light-receiving member for electrophotography having sensitivity to electromagnetic waves such as light [herein used in a broad sense, including ultraviolet rays, visible light, infrared rays, X-rays, and .gamma.-rays].
2. Related Background Art
In the field of image formation, photoconductive materials which form light-receiving layers in light-receiving members for electrophotography are required to have a high sensitivity, a high SN ratio [Photocurrent (Ip)/Dark current (Id)], absorption spectral characteristics matching to those of electromagnetic waves to be irradiated, a rapid response to light, a desired dark resistance value as well as safety to human bodies during usage. Particularly, in the case of a light-receiving member for electrophotography to be assembled in an electrophotographic device to be used in an office as office apparatus, the aforesaid safety characteristic is very important.
From the standpoint as mentioned above, amorphous silicon [hereinafter represented as A-Si]has recently attracted attention as a photoconductive material. For example, German OLS Nos. 2746967 and 2855718 disclose applications of A-Si for use in light-receiving members for electrophotography.
Under the present situation, although the light-receiving members for electrophotography having light-receiving layers constituted of A-Si of the prior art have been attempted to be improved respectively and individually with respect to electrical, optical, photoconductive characteristics such as dark resistance value, photosensitivity, response to light and environmental characteristics in use and further with respect to stability with lapse of time and durability, there still remains room to be further improved in overall characteristics.
For instance, when improvements to higher photosensitivity and higher dark resistance were scheduled to be effected at the same time in light-receiving members, residual potential was frequently observed to remain during use thereof. When such a light-receiving member was repeatedly used for a long time, various inconveniences were caused such as accumulation of fatigue by repeated uses or the so called ghost phenomenon wherein residual images were formed.
Also, when constituting the light-receiving layer of A-Si material, the photoconductive member may contain as constituent atoms hydrogen atoms or halogen atoms such as fluorine atoms, chlorine atoms, etc., for improving their electrical, photoconductive characteristics, boron atoms, phosphorus atoms, etc., for controlling the electroconduction type as well as other atoms for improving other characteristics. Depending on the manner in which these constituent atoms are contained, there may sometimes be caused problems with respect to electrical, photoconductive characteristics or dielectric strength and further stability of the characteristics with lapse of time of the layer formed.
That is, the following inconveniences have frequently occurred. For example, the life of the photocarriers generated by light irradiation in the photoconductive layer constituting the light-receiving layer is not very long, or the image defect which is generally called "blank area" and may be considered to be due to the local discharging breaking phenomenon or the image defect which is generally called "white line" and may be considered to be formed by friction with a cleaning blade are occurred in the image transferred onto a transfer paper. Also, when the light-receiving layer has, for example, a surface layer with a certain film thickness as constituent layer on the surface thereof and the surface layer is substantially transparent to the light used, changes will occur on the reflected spectrum of the surface layer by abrasion with friction for a long time, whereby undesirable changes occurred with lapse of time in many cases particularly with respect to sensitivity, etc. Further, when used in a highly humid atmosphere or used immediately after being left to stand in a highly humid atmosphere for a long time, the so-called faint image was frequently formed.
Thus, it is required in designing of a light-receiving member to make elaborations about layer constitutions, chemical compositions of the respective layers, preparation methods, etc., so as to solve all of the problems as mentioned above along with the improvement of A-Si materials per se.